Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
m = []
m.append('#'*(W+2))
white = 0
for i in range(H):
  s = input()
  m.append(list('#' + s + '#'))
  white += s.count('.')
m.append('#'*(W+2))
 
op = set([(1, 1)])
dist = 0
while len(op) > 0:
  dist += 1
  next_op = set()
  for y, x in op:
    m[y][x] = dist
    if (y, x) == (H, W):
      print(white - dist)
      exit()
 
    for dx,dy in [0,1],[0,-1],[1,0],[-1,0]:
      if m[y-dy][x-dx] == '.':
        next_op.add((y-dy,x-dx))
  op = next_op
 
print('-1')